You've done a lot of interesting mapping work and I plan to explore your site in greater detail. Thanks for the link!

I've heard of but have never used QGIS, mostly because I haven't found a need for it (yet). However, you've opened my eyes to its possibilities.

Although it isn't as comprehensive a mapping tool as QGIS, Alpinequest has very impressive map-handling abilities. I can select several (online) maps, layer them, easily adjust the opacity of each layer, and then (optionally) download the whole shebang for offline use.

Here's an example with three layers ("Base Map" is a default layer):

Caltopo Slope Shading (45%)

Strava Bike Heat Map (45%)

Thunder Forest Outdoors (100%)

If I now want an offline version of this "layer cake", I specify the area I want, the number of zoom levels, and then have Alpinequest download it. Easy-peasy! I now have a custom map I can use offline.

FWIW, Locus Map's "LoMaps" are derived from OpenStreetMap and are vector based. They also include a DEM (SRTM; or download and use another source) which the app can use for map shading. It offers three shading palettes (hill shading, slopes, and colored elevation) or you can define a custom one.

Alpinequest recently added the ability to auto-download a DEM for whatever area of map you are currently viewing. It also uses it for map shading.

Locus Map can also use the DEM to calculate a trackpoint's altitude or the entire track's ascent and descent. I've found this to be very useful given that GPS vertical measurements aren't as precise as a barometric altimeter (and my phone doesn't have one). The app gives you many ways to use a DEM for determining altitude.